I then flycut the heads to get the desired chamber CC’s (with. This means that the chamber is opened up all the way around, making for a much clearer entry for gasses into the cylinder (and exit for the exhaust). I then blend all this together, smoothing all imperfections and casting marks. I also unshroud the valves by opening the sides of the chamber up to the cylinder bore diameter. I like to lay back both the plug side and non-plug side of the chamber by widening the angles. Deep combustion chambers are another problem, as they tend to shroud the valves giving very little room for flow around the valve into the chamber. Too much deck height is a bad thing, resulting in loss of turbulence at TDC when the mixture is ignited and reduce combustion efficiency. If the heads are used, the do the port work first. When working around the valve seat, take extreme care not to accidentally nick the 45 degree angle in the set, or you will be taking the head to the machine shop for dressing the seat. Take time to blend the port and chamber until the step (mismatch) is gone, using your finger to feel for imperfections. There is usually a mismatch of metal in the port and in the combustion chamber. The valve seats are steel inserts pressed into the aluminum casting. I have access to some really nice grinding stones at work and have good success grinding the valve angles by hand, with the exception of the sealing 45 degree angle. You can pay a professional to do this work. A good 3-4-5-angle valve job will enhance the flow improvement even more. The use of stainless steel valves will always improve flow over standard stock valves, as they have a much tighter radius on the backside, allowing for less obstruction at the opening when the valves are open at low lifts. These steps apply to any head of any type: This is necessary for turbos under high boost, however I do not recommend this for a normally aspirated motor, as it will shorten valve guide life). (Note: for the purposes of this article, the heads pictured are for a turbo motor, and have the exhaust guide bosses removed. This process usually takes approximately 10-20 hrs. To keep things the identical, I like to do one step at a time to all 4 ports before moving on to the next step. These are all available to fit a Dremel Moto tool, available at any well-equipped hobby or hardware store. For finishing, I use a sanding roll and small flap wheels (80grit). I like use a rotary file of different shapes (ball, acorn, and tulip shape). Don’t expect your heads to flow as well as a professional’s would. Their trade is truly one of a Black Art form. My sources are Bill Fisher’s How to Hotrod VW Engines (1970), various articles, and my own personal experimentation. Heads with larger valves should have much more porting work done in order to flow to their full potential. These include the 040, 043, and 044, with either stock or 40mm x 35.5mm valves. This is a description of basic porting techniques used to port a stock VW casting, Type 1 heads. Follow along as Thomas Simpson walks you through the basics of head porting. But what if your budget is not within the “guru” price range? Noticeable gains can still be made by the do-it-yourselfer through careful portwork and attention to detail. The total investment in the cylinder heads of a high performance engine can represent a significant portion of the entire engine budget, and in the search for horsepower, you can’t go wrong ordering a set of heads from one of the cylinder head gurus. One of the most important rules of high performance building is to remember that the horsepower is in the heads. Why does one person’s 1914cc engine outperform another’s 2275cc engine? The answer often lies in the cylinder heads. Editor’s note: No matter what type of engine you are building, weather it is a mildly-tuned 1600cc daily driver, or a full-blown 2275cc street-n-strip monster, one of the most important ingredients is the cylinder heads.
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